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Limit range of operations on Indexes in 32-bit mode #4129

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Aug 22, 2024
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Limit range of operations on Indexes in 32-bit mode #4129

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16 changes: 9 additions & 7 deletions lib/compress/zstd_compress_internal.h
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Original file line number Diff line number Diff line change
Expand Up @@ -918,11 +918,12 @@ MEM_STATIC U64 ZSTD_rollingHash_rotate(U64 hash, BYTE toRemove, BYTE toAdd, U64
/*-*************************************
* Round buffer management
***************************************/
#if (ZSTD_WINDOWLOG_MAX_64 > 31)
# error "ZSTD_WINDOWLOG_MAX is too large : would overflow ZSTD_CURRENT_MAX"
#endif
/* Max current allowed */
#define ZSTD_CURRENT_MAX ((3U << 29) + (1U << ZSTD_WINDOWLOG_MAX))
/* Max @current value allowed:
* In 32-bit mode: we want to avoid crossing the 2 GB limit,
* reducing risks of side effects in case of signed operations on indexes.
* In 64-bit mode: we want to ensure that adding the maximum job size (512 MB)
* doesn't overflow U32 index capacity (4 GB) */
#define ZSTD_CURRENT_MAX (MEM_64bits() ? 3500U MB : 2000U MB)
/* Maximum chunk size before overflow correction needs to be called again */
#define ZSTD_CHUNKSIZE_MAX \
( ((U32)-1) /* Maximum ending current index */ \
Expand Down Expand Up @@ -1274,8 +1275,9 @@ U32 ZSTD_window_update(ZSTD_window_t* window,
/* if input and dictionary overlap : reduce dictionary (area presumed modified by input) */
if ( (ip+srcSize > window->dictBase + window->lowLimit)
& (ip < window->dictBase + window->dictLimit)) {
ptrdiff_t const highInputIdx = (ip + srcSize) - window->dictBase;
U32 const lowLimitMax = (highInputIdx > (ptrdiff_t)window->dictLimit) ? window->dictLimit : (U32)highInputIdx;
size_t const highInputIdx = (size_t)((ip + srcSize) - window->dictBase);
U32 const lowLimitMax = (highInputIdx > (size_t)window->dictLimit) ? window->dictLimit : (U32)highInputIdx;
assert(highInputIdx < UINT_MAX);
window->lowLimit = lowLimitMax;
DEBUGLOG(5, "Overlapping extDict and input : new lowLimit = %u", window->lowLimit);
}
Expand Down